6 CO2 (Carbon Dioxide) Greenhouse gas (heavier than air) Global warmingOcean acidification (carbonic acid)CO2 is a well known Greenhouse gas that is considered responsible for global warming and acid rain which results in acifidication of large bodies of water.

7 Physiology of MetabolismOxygen  Lungs  alveoli  bloodOxygenBreathCO2Muscles + OrgansLungsOxygenCO2CellsThe body uses oxygen, glucose and water to produce energy. The byproduct of this process (metabolism) is CO2. The more energy produced, the more CO2. The less metabolism (less energy produced), the less CO2.ENERGYBloodOxygen+GlucoseCO27

8 Carbon DioxideOxygen (O2) enters the body through the lungs and is used to produce energyThis process is called metabolismCarbon Dioxide (CO2) is the waste product of metabolism

10 CO2 In the Blood CO2 is your drive to breathe  CO2 causes air hungerGoal is to maintain PaCO2 at 40Body adjusts respiratory rate & depthOxygen does not affect respirationsCO2 is the gas that produces the respiratory drive. When CO2 levels increase, people experience air hunger. The body responds to increased CO2 in the blood by increasing respiratory rate and depth. Oxygen levels in the blood do not affect respirations in the vast majority of people.

11 Question:What would happen if you injected CO2 into the blood? Respiratory rate and depth would 

12 Question:Why do swimmers who hyperventilate loose consciousness underwater?  CO2 eliminates the drive to breatheSwimmers who deliberately hyperventilate in order to hold their breath underwater for longer periods of time sometimes loose consciousness. The mechanism for this phenomena is marked reduction of CO2 induced by hyperventilation, resulting in loss of drive to breathe and elimination of air hunger. When the oxygen level in the blood drops below that needed to maintain consciousness, the swimmer passes out. The usual warning that s/he should surface to breathe is bypassed by hyperventilating before diving into the water.

13 Turns yellow when CO2 is detectedMeasuring Exhaled CO2ColorimetricCapnometryCapnographyIn the 1970’s colorimetric devices were used to measure CO2. These devices use a piece of pH paper positioned in the airway to indicate the presence of CO2 by changing from purple to yellow.Turns yellow when CO2 is detected

14 Colorimetric Pros Cons Accurate Secretions Cheap (~$10-15)Changes color when CO2 presentWork for 2+ hoursDisposableConsSecretionsNot quantitativeAdds dead spaceFalse positivesHard to read at nightColorimetric devices are inexpensive, disposable and usually last for at least 2 hours (sometimes as long as 24 hours). They can be damaged when the pH paper gets wet from secretions resulting in false positive CO2 readings. It is difficult to quantify the amount of CO2 using a colorimetric device, although the degree of color change can suggest various levels of CO2. In small patients, the dead space added to the airway by placing a CO2 detector can be excessive.

15 Measuring Exhaled CO2 Capnometry Colorimetric CapnographySecond generation CO2 measuring devices were capnometers. These provide a respiratory rate and digital measurement of CO2 as well as a bar graph with each breath.

16 Capnometry Pros Cons Numeric value + RR PortableCheaper than waveform capnographyConsNo waveformDoes not trendBulky adapter/unitCapnometers are portable, provide more information than colorimetric devices but lack a waveform which would be helpful for visualizing trends and tend to be somewhat bulky (which means they may add additional weight to an advanced airway, potentially dislodging an endotracheal tube). In 2012, the EMMA Capnometer (Masimo Corp., Irvine CA) was redesigned to include a waveform which transformed the capnometer into a waveform capnography device.PHASEINEMMA™ (Masimo)

17 Measuring Exhaled CO2 Capnography Colorimetric CapnometryWaveform capnography is the third and current generation of devices used to measure exhaled CO2.

18 Capnography Pros Cons Numeric value + RR Waveform TrendingVery accurateConsExpensiveFragileWarm-up time (some units)SecretionsTemperature sensitive (some)Waveform capnography is extremely accurate but expensive, fragile, prone to clogging from respiratory secretions and, in some cases, require time to warm up prior to use and/or are affected by environmental or patient temperature extremes.

20 Capnography TechnologiesSidestream (1st generation)Sensor in remote locationSamples gas from circuit ( mL/min)Mainstream (2nd generation)Sensor in the airwayFirst generation CO2 technologies were sidestream devices. The sensor was in a remote location and sampled large amounts of gas from the respiratory circuit in order to make measurements. This large volume sampling mandated that sidestream analyzers have moisture traps. Second generation devices moved the sensor into the airway itself.

21 Capnography TechnologiesMicrostream® (next generation)Sensor in remote locationSamples only 50 mL/min from circuitThird generation devices (Microstream) work in a similar fashion to sidestream devices but sample significantly less air from the line, eliminating the need for a large moisture trap and allowing use in very small patients and in spontaneously breathing patients. Moisture is trapped by a filter placed in the Microstream connector.

22 SpO2 versus EtCO2The is a significant difference between pulse oximetry and capnography.

23 Oxygenation and VentilationOxygenation (Pulse Ox)O2 for metabolismSpO2 measures % of O2 in RBCsReflects changes in oxygenation within 5 minutesVentilation (Capnography)CO2 from metabolismEtCO2 measures exhaled CO2 at point of exitReflects changes in ventilation within 10 secondsA quick summary of the two physiological processes. They require different monitoring modalities which are complimentary measures of your patient’s status.

26 Pulse OximetryFirst generation pulse oximetry has been known to produce a reading and a waveform even when not connected to patient.

27 Pulse OximetryFirst generation pulse oximetry sometimes produces “weird” readings. Seemingly healthy patients may exhibit very low saturations. When a blood gas is drawn, the actual oxygen saturation is found to be normal.

28 Model of Light Absorption At Measurement Site Without MotionAC Variable light absorption due pulsatile volume of arterial bloodDC Constant light absorption due to non-pulsatile arterial blood.DC Constant light absorption due to venous blood.DC Constant light absorption due to tissue, bone, ...AbsorptionTimeIMPORTANT POINTS on the original design of pulse oximetry:AC (alternating current) represents the arterial blood that is moving inside the body.DC (direct current) represents the blood and other components that are not moving inside the body.This is the Aoyagi model that assumed the only component that moves inside the body is the pulsating arterial blood.One of the reasons for many false alarms for this model is that it does not accurately predict what is occurring inside the body. Aoyagi assumed that the only thing that moves in the body is pulsating arterial blood. So, when he uses the pulse for his in vivo calibration, if other components move, the reading will be in error.

29 Model of Light Absorption At Measurement Site With MotionAC Variable light absorption due pulsatile volume of arterial bloodDC Constant light absorption due to non-pulsatile arterial blood.AC Variable light absorption due to moving venous bloodDC Constant light absorption due to venous blood.DC Constant light absorption due to tissue, bone ...TimeAbsorptionIMPORTANT POINTSMoving (AC) venous blood is the main contributor to motion artifact.This was not predicted by the Aoyagi design.This effect is significant in monitored patients and causes erroneous values.Aoyagi’s model was correct as long as the patient did not move. But as soon as the patient proceeded with even normal daily activity the above moving venous blood (AC) was introduced and affected the reading.

30 Influence of Perfusion on Accuracy of Conventional Pulse Oximetry During MotionGood Perfusion (Conventional PO)SpaO2=98SpO2=93SpvO2=88Poor Perfusion (Conventional PO)IMPORTANT POINTSVenous averaging is a significant clinical problem.When the perfusion is good the effect is only slightly observed.When perfusion is very poor, the effect can be dramatic and cause an inappropriate clinical response.Common Cause of a False Alarm:This effect can be demonstrated with a motion low perfusion ice water demonstration. By cooling the hand using a glass of ice water and then moving the cold hand with a conventional sensor attached, poor peripheral perfusion (the second example above) can be simulated. The moving venous blood causes a conventional oximeter to average the arterial and venous values together and report a value between arterial and venous. This erroneous value will set off alarms, bring the clinician to the bedside, and potentially waste caregiver time responding to the situation. If this situation persists, the caregiver may silence or turn off the alarms and put the patient at risk for a true desaturation event later.SpaO2=98SpO2=74SpvO2=50

31 Conventional Pulse Oximetry AlgorithmDigitized, Filtered & NormalizedR/IRPost Processor% SaturationR & IRMEASUREMENTTCONFIDENCE3 options during motion or low perfusion:Freeze last good valueLengthen averaging cycleZero outIn conventional pulse oximetry, the incoming red and infrared signals are received from the photodetector. In many of the newer oximeters, the signals are digitized. The signals then pass through band filters to remove much of the unwanted artifact above and below the signal bandwidth. These filters address external noise sources like electrical devices or mechanical artifact. After the signals have been filtered, a red to infrared ratio is calculated. This calculated ratio is compared to a “look up” table that converts the red to infrared ratio to a corresponding SpO2%.Once the SpO2 is calculated, the oximeter’s decision matrix must decide if the data is reportable or not.If the decision is “Yes, it looks good” the SpO2 and pulse rate are reported. If the decision is ‘No, this looks questionable” , there are a few paths the oximeter can take depending on what the oximeter manufacturer has programmed into the system. Some oximeters might “lie” and freeze or continue to display the last valid SpO2 and pulse rate value it recorded for one minute or longer, regardless of the patient’s changing clinical status. Others might go into a longer averaging cycle “hoping” that whatever was interfering with the signal will just go away or self resolve. Some device will just “zero out” and give up. Regardless of whether the oximeter chooses to “lie, hope or give up” the clinician no longer has reliable pulse oximetry data, often in situations when it is needed the most..

32 Next Generation Pulse OximetryEach manufacturer has designed confidence based algorithms to improve the accuracy of their pulse oximetry. Nellcor (now Covidien) uses an algorithm that focuses on the accuracy of the pulse rate being detected by the oximeter.

33 Next Generation Pulse OximetryPhilips also uses a confidence based algorithm.

34 Masimo SET: Signal Extraction TechnologyR/IR (Conventional Pulse Oximetry)Confidence Based Arbitrator% % 97% 100%SpO2%Post ProcessorDigitized, Filtered & Normalized% SaturationSSTTMProprietary Algorithm 4DSTSET – 97%DSTTMFSTTMMEASUREMENTCONFIDENCER & IRIMPORTANT POINTS1) Signal Extraction Technology uses a variety of algorithms or engines. Each is designed for a different type of signal noise.2) The confidence based arbitrator determines which engines are providing the most accurate saturation value and displays that value.3) Discrete Saturation Transform is the most powerful engine and can remove the noise caused by moving venous blood which is the number one cause of motion artifact.While this slide may look complicated, focus on the R/IR, DST engines and the Confidence based Arbitrator. The R/IR engine is the same as other conventional pulse oximeters and reads accurately about 50% of the time. When patients are healthy, well perfused and without motion artifact, most pulse oximeters can determine the saturation.As was discussed earlier, DST can remove the number one cause of motion artifact which is moving venous blood. It is used about 25 % of the time and eliminates the false reading associated with venous blood artifact.Finally, the confidence based arbitrator gives SET the ability to change as patient conditions change. It can select from any one or a combination of the engines and accurately determine the saturation in spite of challenging conditions.SET “Parallel Engines”

36 Carbon Monoxide (CO) Gas: Physical Properties: Colorless OdorlessTastelessNonirritatingPhysical Properties:Vapor Density = 0.97LEL/UEL = 12.5 – 74%IDLH = 1200 ppmPhysical properties of carbon monoxide (a dyshemoglobin): Vapor Density is just about equal to that of the ambient air. This means that rather than rising to the highest point (lighter than air) or sinking to the low lying areas, CO acts like the ambient air and travels through the entire occupancy, following natural air flow. This translates to poisonous gasses presenting themselves across the occupancy, rather than lingering near the offending source, and exposure should never be ruled out because the occupants’ report that they were not near fuel fired appliances. The flammability range, expressed as the range between the Upper Explosive Limits (UEL) and the Lower Explosive Limits (LEL) is rather wide, therefore efforts to control ignition sources should be undertaken. The Immediately Dangerous to Life and Health is expressed as the IDLH in parts per million. While this number may seem a bit on the high side, EMS providers should take caution as they typically do not respond with self-contained breathing apparatus (SCBA) and atmospheric levels in an enclosed environment can climb rather quickly. The bond length is pm.

37 Limitations of Pulse OximetryConventional pulse oximetry can not distinguish between COHb and O2HbFrom Conventional Pulse OximeterSpCO-SpO2 Gap:The fractional difference between actual SaO2 and display of SpO (2 wavelength oximetry) in presence of carboxyhemoglobinFrom invasive CO-Oximeter Blood SampleIMPORTANT POINTSThe arterial oxygen saturation (SpO2) from conventional two-wavelength pulse oximetry is inaccurate (often significantly inaccurate) in the presence of CO poisoning.Two-wavelength pulse oximeters actually count carboxyhemoglobin as oxyhemoglobinThe reported functional value often lends a false sense of security that the patients oxygenation status is good, as SpO2 may read normal even when significant COHb is poisoning the patient.A standard 2 wavelength oximeter adds to the problem. They only read 2 parameters, which result in a ratio of the oxyhemoglobin to the hemoglobin that is available for binding . This is called the Functional value and does not decreaseto any significant degree, as shown by the graph above, even when exposed to high levels of CO. In this experiment a dog is exposed to CO and the pulse oximeter only decreases slightly to 90% when the actual oxyhemoglobin saturation is 30%. This actual saturation value is called the fractional saturation. Fractional saturation is not subjected to this false reading and would have read 30% in this situation.Barker SJ, Tremper KK. The Effect of Carbon Monoxide Inhalation on Pulse Oximetry and Transcutaneous PO2. Anesthesiology 1987; 66:

38 Pulse CO-oximetryThe RAD-57 is a pulse CO-oximeter. It is able to measure both oxygen (oxyhemoglobin) and carbon monoxide (carboxyhemoglobin) in the blood.

39 Pulse CO-oximetry Uses multiple wavelengths of lightDifferentiates CO from O2This is accomplished by using multiple (8+) wavelengths of light, some visible and some invisible spectra.

41 Protect from ambient lightSpCO User ConcernsMultiple wavelengths of light (8+) =Probe Placement:Probe fits the fingerCentered over nail bedVisible spectrum light =Protect from ambient lightSunlight, strobes, etc.The fact that CO is measured in a visible spectrum of light means that it is particularly susceptible to interference from visible light. Because the technology is using multiple wavelengths of light, probe positioning and probe size is much more important than a conventional pulse oximeter (which uses only 2 beams of light). If the probe is misplaced (or too large for the finger), light will pass around the finger (instead of passing through the finger). This may result in false CO readings.

44 Endotracheal IntubationEndotracheal intubation is a high risk procedure.

45 What Should Happen Lungs (Good) $tomach (Bad, Very Bad)A missed esophageal intubation can be catastrophic.$tomach (Bad, Very Bad)

46 Anesthesia LitigationAnesthesiologists in the 1960’s and 1970’s had the highest malpractice rates of any medical profession, largely due to lawsuits for unrecognized esophageal intubations.46

47 Respiratory Damaging EventsCapnography IntroducedBeginning in the 1980’s, anesthesiologists using end tidal CO2 were able to reduce their claims for respiratory damaging events. Today, malpractice insurance premiums for anesthesiology providers are among the lowest in the medical community.American Society for Anesthesiologists: Closed Claims Project Database, 201047

48 #1 Capnography Use for EMS:Paramedics have the same risks as anesthesiologists. This is the number one use of end tidal CO2 monitoring.

50 Intubated Patient Airway adapter plugs into LifePak®Be sure adapter is tightly attachedIf not seated, waveform may flattenAn important consideration in using capnography is to assure that the connector is tightly screwed into the monitor. If the connector is not firmly seated, atmospheric air will be pulled into the monitor from around the connector, resulting in poor or no end-tidal CO readings.

52 Capnography WaveformsThe higher the waveform, the more CO2Normal EtCO2 is 35 – 45 mmHg (usually the same as arterial CO2)45The height of the waveform equates to the amount of CO2.

53 Capnography WaveformsThe length of the waveform corresponds to respiratory rateHyperventilation45The length of the waveform corresponds to the respiratory rate. The shorted the waveform, the faster the rate.45Hypoventilation

54 Inspiration or manual ventilation with a bag-valve-mask or ventilatorCapnography WaveformInspiration or manual ventilation with a bag-valve-mask or ventilator54

63 IntubationYou have intubated a 36 year old motorcyclist laying in the roadwayHR 128, RR 14 by BVM, SpO2 99%Esophageal intubation6 breaths to evacuate gastric CO2The standard practice for “washing out” gastric CO2 is to provide 6 breaths and then measure CO2. If the tube is in the esophagus, 6 breaths will wash out any gastric CO2.

64 SpO2 will not drop for several minutes (5+ minutes)What about the Pulse Ox?Sp0298Pulse oximetry takes considerably longer to drop once breathing ceases.SpO2 will not drop for several minutes (5+ minutes)

65 Intubation You re-intubate the motorcyclistThis is the capnography waveform:Is the tube in?Is the ventilation rate and depth appropriate?mmHgYes, the tube is now appropriately located in the trachea. The respiratory rate of 16 and depth (size of breaths) is adequate as the exhaled CO2 is 39, midway between the target of mmHg.

66 During TransportEnroute to the trauma center, you observe this on the capnography:What happened?When is this most likely to occur?Tubes most commonly displace during patient movementThe tube came out. This most commonly occurs with patient movement, often at the moment the patient is transferred to the ED stretcher. This is a major reason for documenting the presence of a good capnography waveform following endotracheal intubation and during transport.

67 Ventilator TransportYou are moving a 23 yo GSW to the head from a community ED to a neurosurgical ICUHe is intubated and sedated:EtCO2 = 35, RR = 24“Curare Cleft” = diaphragmatic movement (breathing over drugs)

69 Ventilator Transport You are moving a ventilated patientThe patient appears short of breathWaveform does not return to zeroBaseline gradually increasingThis is called “rebreathing”Rebreathing is more often seen in patients on mechanical ventilation and is often association either with excessive respiratory rates or faulty ventilator equipment. It is sometimes referred to as “breath stacking”

79 3. EtCO2 to detect ROSC (Return Of Spontaneous Circulation)90 pre-hospital intubated arrest patients16 survivors13 survivors: rapid rise in exhaled CO2 was the earliest indicator of ROSCBefore pulse or blood pressure were palpableUsing an EtCO2 of 10 mmHg or less as a theoretical threshold to predict death in the field successfully discriminated between the 16 survivors to hospital admission (those that achieved return of spontaneous circulation) and 75 prehospital deaths. Of the 16 survivors to hospital admission, 9 died in the hospital, and 7 were discharged from the hospital alive. In 13 of the 16 survivors, the first evidence of return of spontaneous circulation, before a palpable pulse or blood pressure, was a rising ETCO2.Wayne MA, Levine RL, Miller CC. “Use of End-tidal Carbon Dioxide to Predict Outcome in Prehospital Cardiac Arrest” . Annals of Emergency Medicine. 1995; 25(6):Levine RL., Wayne MA., Miller CC. “End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest.” New England Journal of Medicine. 1997;337(5):

80 3. EtCO2 to detect ROSC Question: Would bicarbonate  EtCO2?ROSC is associated with significantly increases EtCO2. Administering bicarb will transiently elevate CO2 as acids buffered by the bicarbonate in the blood are eliminated as CO2.Question: Would bicarbonate  EtCO2?Answer: Yes

86 Unconscious16 yo found unresponsive in high school locker room – unknown hxHypoventilation (? pharmaceutical)Use capnography on EVERY patient you treat with narcotics!The best way to observe respiratory effort and rate is with capnography. Every patient given narcotics should have continuous waveform capnography monitored.

87 Difficulty Breathing 14 yo asthmatic – severely SOB HyperventilationNo evidence of airway obstruction or air trappingFast respiratory rates are difficult for the capnography equipment to accurately track. Waveforms then, loose their crisp appearance in pediatric and neonatal patients as well as in adults with high respiratory rates.

91 Perfusion and pH Cardiac arrest = no CO2Capnography reflects perfusion cardiac output =  EtCO2CO2 is transported in the blood as bicarbonate (HCO3)In severe acidosis,  HCO3 =  EtCO2In cardiac arrest, no CO2 is produced. In profound metabolic acidosis, CO2 is used in the blood to combine with the acids and is not exhaled. The lower the bicarb level in the blood (i.e., the more acidotic the patient) the lower the exhaled CO2 will be.

92 Post Cardiac Arrest PatientYou have resuscitated a 47 yo pt. found in v-fib on a city busThe patient is unresponsive, ventilated by BVM; pulses are weakSuspect falling cardiac output!

93 17 yo pt. in DKAYou are called to a physician office to transport a patient in DKAThe patient is alert and oriented; blood sugar is reportedly 880This is another waveform tracing from a 17-year-old in diabetic ketoacidosis. Note here again the extremely low cardiac arrest level EtCO2 of 6 millimeters of mercury, and a corresponsive pH of This waveform tracing illustrates how sensitive and accurate capnography is in detecting conditions of metabolic acidosis.

94 General Weakness PatientYou are called to see a 75 yo heart failure pt. with general weaknessShe is cool, BP 80/50, HR 128 afibWhat does the capnography say?Low perfusion associated with lactic acidosis will produce a low EtCO2!Cardiogenic Shock!